The government said it could not protect foreign mission personnel in the event of conflict on the Korean peninsula, Xinhua, the official Chinese news agency, reported.
Russian Foreign Minister Sergei Lavrov, on a visit to Uzbekistan, said his government has not made a decision and wants to "clarify" the situation. The British Foreign Office also said it is considering what to do, the BBC reported.
There were also reports Friday that North Korea had moved two missiles to launchers, the BBC said. South Korean officials told Yonhap news agency two ships with Aegis missile defense systems are monitoring North Korea.
"If the North fires off a missile, we will trace its trajectory," an unnamed official said.
On Thursday, the State Department defended the robust U.S. response to North Korean threats but a Pentagon official said announcing the response may have fueled tensions.
"When you have a country that is making the kinds of bellicose threats that they are making and taking the steps that they are taking, and when you have allies and treaty commitments, you have to take it seriously -- you don't have any other choice," State Department spokeswoman Victoria Nuland told reporters.
"So the moves that we have been making are designed to ensure and to reassure the American people and our allies that we can defend the United States, that we will, and that we can defend our allies," she said.
"So, from that perspective, it was the ratcheting up of tensions on the DPRK's side that caused us to need to shore up our own defense posture," she said.
DPRK stands for Democratic People's Republic of Korea, commonly known as North Korea.
But Pentagon officials told CNN Washington may have contributed to the escalating tensions with announcements of U.S. military deployments in response to Pyongyang's bellicose statements.
"We accused the North Koreans of amping things up -- now we are worried we did the same thing," a Defense Department official told the network.
As a result, "we are trying to turn the volume down ... ratchet back the rhetoric," the official said, referring to such matters as where and how U.S. military hardware are deployed in the region.
The Pentagon said Wednesday the U.S. Army was speeding the sophisticated Terminal High Altitude Area Defense, or THAAD, missile defense system to Guam two years ahead of schedule to protect U.S. forces in the Pacific from a possible North Korean attack.
It earlier announced it flew nuclear-capable B-2 Spirit stealth bombers, Cold War-era B-52 Stratofortress strategic bombers and F-22 Raptor stealth jet fighters over South Korea in joint military exercises with Seoul.
The North announced Tuesday it would resume operations to produce weapons-grade plutonium at a formerly shuttered nuclear reactor at its Yongbyon Nuclear Scientific Research Center.
Pyongyang also escalated the war of words Thursday, warning Washington it would "take powerful, practical military counteractions" against the B-2 and B-52 bombers and F-22 jet fighters, which it described as a threat.
"The moment of explosion is approaching fast," the general staff of the North Korean army said in a statement carried by the North's official Korean Central News Agency. "The U.S. had better ponder over the prevailing grave situation."
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